Smoke generator



Aug- 12, 1952 c. s. MCMULLEN 2,606,546

SMOKE GENERATOR Filed Deo. 25. 194'? 5 sheet-sneet 1 f ATTORNEY Aug 12,1952 c. s. MGMULLEN SMOKE GENERATOR 3 Sheets-Sheet 2 Filed Deo. 25, 1947lNvENToR CzadS/llwalkn/ ATTORNEY 5 Sheets-Sheet 5 INVNTOR awMCH/mm BY yATTORNEY c. s.' MCMULLEN SMOKE GENERATOR Aug. 12,1952

Filed Dec. 25 1947 Patented Aug. 12, 1952 UNITED STATES PATENT OFFICESMOKE GENERATOR Claud S. McMullen, New York, N. Y., assignor to NationalSmokehouse Equipment, Inc., Clifton, N. J., a corporation of New JerseyApplication December 23, 1947, Serial No. 793,502

(Cl. 12S-59.5)

6 Claims. 1

This invention relates to a'srnoke generator for use in producing smokefor the smoke curing and preserving of comestibles such as meat or fish.

Smoke generators heretofore available have operated on the principle ofsupplying to a relatively deep bed of sawdust an amount of airinsuicient to support combustion of the sawdust and causing the sawdustto smolder to generate the smoke which, after washing, if desired, isfed to the smoke houses. These generators produce smoke of varyingdensity with consequent variation in the color or other properties ofthe comestibles cured or preserved by treatment therewith. Furthermore,such generators require frequent attention and convert only a minorportion of the sawdust to smoke, the remainder ci the sawdust beingrequired for combustionpurposes. Moreover, such generators arerelatively inflexible, i. e., they can be operated at full capacity ornot at al1. In those cases in which a smoke generator is employed tosupply smoke for a plurality of smoke houses and for some reason it isdesired to supply smoke to only some of the houses, the iniexibility ofthe smoke generator presents a serious problem. Usually the smokegenerator is run at its full capacity and the smoke supplied to thesmaller number of smoke houses; under these conditions comestibles aresubjected to a correspondingly greater volume of smoke with consequentdeleterious effect on the product and uneconomic utilization of thesawdust employed to produce the smoke.

It is an object of this invention to provide a smoke generator forproducing smoke for treatment of comestibles which generator produces auniform volume of substantially constant density smoke, can readily beadjusted to produce any desired volume of such smoke or to produce smokeof different density, if desired, requires a minimum of attention by theoperator, is compact and simple in design and efficient in operation.

Other objects and advantages of this invention will be apparent from thefollowing detailed description thereof.

In accordance with this invention, a controlled miount of relativelycool moist sawdust is fed on to a grate or other support to form arelatively thin layer of sawdust thereon and a blast of air or otheroxygen containing gas is introduced into contact with this thin layer ofsawdust to consume the sawdust substantially at the same rate as it isfed on to the support, thus continuously generating a uniform volume ofsmoke per unit weight of sawdust fed on to the support. The amount ofoxygen containing gas thus contacted with the sawdust is in excess ofthe stoichiometric amount required to support combustion thereof.

In accordance with a preferred embodiment of the invention, the smokegenerator comprises an oblong housing. At one end of this housingdisposed in side'by si'de relationship are a sawdust receivingcompartment and a smoke generator compartment. These compartments extendalmost the full length of the oblong housing and occupy the majorportion of the volume of the housing, the sawdust receiving compartmentbeing the larger of the two to provide a substantial s-torage ofsawdust. The sawdust receiving compartment is suitably insulated so thatthe sawdust therein is not heated by the heat generated within the smokegenerating compartment but is maintained in cooled moist condition inwhich condition it is fed continuously at a controlled rate to the smokegenerating compartment. The smoke generating compartment contains agrate on to which sawdust is fed from the sawdust receiving compartment.A ilue extends the full length of the smoke generating compartment nearits top for receiving the smoke generated.

At the other end of the oblong housing are disposed in side by siderelationship a smoke receiving passage communicating with the flue and asettling out and cooling passage communicating with the smoke receivingpassage. A fan is provided for exhausting smoke from the smoke receivingpassage and introducing it into the settling out and cooling passage.provides the forced draft which causes atmospheric air to flow underrelatively high velocity into contact with the sawdust to generatesmokeas hereinabove described, which smoke iiows through the flue, the smokereceiving passage and the fan, and is pumped by the fan into and throughthe settling out and cooling passage into the smoke discharge port atthe exitend of the latter passage. A spray of water is fed to the fanand serves to keep the fan shaft and bearings cool and to quench anysparks which may be carried off by the smoke into the fan. This water isbroken up into ne particles by the fan, which particles are dispersed inthe stream of smoke to cool the smoke stream. The fan also communicateswith a channel leading into the atmosphere. This channel and thatconnecting the fan with the smoke Yreceiving passage are each providedwith a damper which may be controlled manually or automatically toregulate the amount of air mixed with the smoke to produce a smoke Thisfan also stream of any desired density. The stream thus produced isintroduced into the settling out and cooling passage. In its fiowthrough the settling out and cooling passage tarry material and othersuspended material are removed from the smoke stream, settle into a bodyof water maintained at the base of this passage, and are flushedV out ofthe smoke generator.

In the accompanying drawingsforming a part of this specification andsh-owing for purposes of exemplication a preferred form of thisinvention without limiting the claimed invention to such illustrativeinstance:

Figure 1 is a perspective viewof a smoke generator embodying thisinvention;

Figure 2 is a plan view of the generator shown in Figure l;

Figure 3 is a vertical section taken in a plane passing through line 3-3on Figure 2;

Figure 4 is a vertical'section, partly in elevation, taken in a planepassing through line 4-4 on Figure 2;

Figure 5 is a horizontal section taken inrplanes passing through line5-5on Figure 3;

Figure 6 is a vertical section taken in a plane passing through line 6-6on Figure 3; and

Figure 7 is a fragmentary vertical section taken in a plane passingthrough line 'I-'I on Figure 4.

In the drawing I indicates an oblong housing f consisting of a frontwall II, back wall I2, and end walls I3 and-I4, desirably of cast ironor steel or other suitable material. This housing is supported onsuitable legs I desirably positioned at each of the corners thereof. Thefront and rear pairs of legs, viewing Figure 1, rest on and desirablyare bolted or otherwise secured to channel irons I6 and I1,respectively, which impart rigidity to the leg support for the housingand carry the entire Weight of the generator.

Disposed at one end of the housing in side by side relationship are asawdust receiving compartment I8 and a smoke generating compartment I9(Figure 3). Both of these compartments, as shown in Figure 5, extendfrom end Wall I4 of the housing to an intermediate wall and occupy amajor portion of the volume of the housing. The top of the sawdustreceiving compartment I8 extends across the full width of the housingI0, is provided with a charging opening 22 normally closed by cover 23equipped with a handle 24 through which opening 22 sawdust may besupplied to compartment I8.

The base of the sawdust receiving compartment I8 is defined by aninclined shelf 25 and a semicylindrical section 26. Wall 21 separatesthe sawdust receiving compartment I9 from the smoke generatingcompartment I9 and is made of suitable high temperature heat insulatingmaterial such as asbestos cement. A longitudinally extending narrow slotor opening `29 places the sawdust receiving compartment I8 incommunication with the smoke generating compartment I9.

Feed of the sawdust through feed slot 29 is acomplished by a cylindricaldrum 30 mounted on a shaft 3l. Drum 30 has approximately 180 of itsperipheral surface removed to form an opening 32 which when in theposition shown in Figure 3, permits the sawdust to enter the drum. Aflange or extension 33 extends above the periphery of the drum the fulllength thereof. This flange, when the drum is rotated, serves to agitatethe cool moist sawdust in compartment IB insuring -iiow of thev sawdustinto the interior of 4 drum 30 through opening 32. As the rotation ofthe drum is continued in the direction indicated by the full line arrowon Figure 3, ange 33 moves through semi-cylindrical section 26 with verylittle clearance between it and the wall of section 25, forcing a layerof sawdust through feed opening 29. In the operation of this feeder aconstant amount of sawdust is fed through opening 29 per revolution ofdrum 30. If it is desired to change the amount of sawdust fed to thesmoke generating compartment I9, it is only necessary to change the rateof rotation of drum 30.

Shaft 3l of drum 30 is mounted for rotation in suitable bearings inwalls I4 and 20 defining the opposite end walls of the sawdust receivingand smoke generating compartments. Rotation of this drum may be effectedby any suitable driving mechanism, for, example that shown in Figure 2involving a bevel gear 34 keyed to shaft 3| and meshing with a bevelgear 35 on a shaft extending from reducing gear box 36. A motor 31drives this shaft through suitable reduction gears disposed in box 36.

The smoke generating compartment I9 desirably has a rebrick top wall 38,a rebrick lined side wall 39 and a firebrick portion 40 in alignmentwith heat insulating wall 2l as shown in Figure 3. A grate 4I issuitably supported on rebrick supports in the base portion ofcompartment I9 just below opening 29 as shown in Figure 3. This gratemay consist of a flat metal plate provided with a number of elongatedslots 42 which as shown in Figure 5 are arranged in three parallel rows,the slots of one row being staggered with respect to those of acontiguous row. The number and size of such elongated slots should besuch as to provide a high velocity of air therethrough in contact withthe relatively thin layer of sawdust supplied to grate 4I by thehereinabove described sawdust feed. A smoke receiving flue 43, desirablymetal lines, is positioned at the top of the smoke generatingcompartment I6 and has an opening 44 running the full length thereofthrough which smoke generated in compartment I6 enters the flue 43. Thisflue conducts the smoke generated in compartment I6 to a smoke receivingpassage 49 hereinafter more fully described and also provides a confinedpath which communicates with the smoke generating compartment throughopening 44. Fan 6I hereinafter described exerts a suction through thispath causing air to enter through slots 42 to support combustion of thesawdust fed on to grate 4I.

Disposed in the front wall II just above grate 4I is a cleanout door 45which when removed gives access to the top of the grate and the feedopening 29. Suitable supports 46, desirably angle irons, are fastened tothe base 47 of the housing and are arranged to removably receive an ashpan 48 into which fall the ashes from grate 4I. This ash pan is readilyremovable so that the ashes may be dumped and the pan replaced, whendesired, on the supports 46.

Flue 43 communicates with a smoke receiving passage 49 desirablypositioned at the opposite end of housing I0 from that containing thecompartments I3 and I9 as shown in Figure 5. A bale 50 (Figures 4 and 6)extends downwardly from near the top of passage 49 across the inlet port5I with which flue 43 communicates. This baille deiiects the smoke in adownward direction and` causes it to flow rst toward the base of passage49 and then upwardly therethrough.

A cleanout opening 52, normally closed by a door 53, is provided justabove the oor or base of passage 49. Suspended material carried by thesmoke stream and settling out therefrom due to change in direction offlow caused by baffle 50 may be removed from time to time, as desired,through opening 52.

A bearing standard 5d is bolted 'or otherwise secured to the top ofhousing Il! as at 55. Fan shaft 56 is rotatably mounted in bearing 5Tcarried by this standard. This fan shaft may be driven through a belt orchain and sprocket drive 58 disposed in a removable housing or guard 59and actuated by the drive mechanism hereinabove described. This fan isdisposed within a housing 62 provided with one passageway 53 (Figure 6)connecting the fan with passage 49, a second passageway 6d communicatingwith the atmosphere, and a third passageway 65 (Figure 4) leading fromthe base porh of desired density. For any given adjustment cf dampers Siand tu, a smoke of constant deiinite density is produced, as will bepointed out more fully hereinafter. If it is desired to change thedensity for any reason, this is accomplished by changing the setting ofdampers fil and 68.

A water spray or jet ill is positioned to discharge water onto the fanbearings as shown in Figure 6. The water thus serves to cool the ianbearings and is dispersed in fine drops by the fan blades into the smokestream flowing through the fan housing functioning to partially coolthis smoke stream. Jet 'Eil is supplied by water from a line l! (Figurel) having a valve l2 therein, provided with a threaded coupling i3 forconnection to any suitable water line, a second valve i4 controllingflow throughl a branch 'l5 leading into a water sump 16 (Figure 4)disposed at the base oi the settling out and cooling passage 55.

A steam jet i is disposed in the passageway 3 and may be turned on whenthe temperature of the smoke is too low, say below 120 F., to introducesteam to raise the temperature to the desired value. Desirably steam jeti5 and water by well known throttling type thermostat controls lld andiilb (Figures l and e) located at the top of passage 65. If thetemperature of the smoke entering passage 5S is too high, the water andsteam iet valves are operated to control the ilow of these media so thatthe temperature of the smoke entering passage 55 is maintained at thedesired constant value. Thus, for example, should the temperature of thesmoke rise, more cooling water is admitted through jet i and should thetemperature fall below the desired value, steam. is turned on, or moresteam admitted through jet lu'. Since the controls 10a and 'mh may be ofany well known type, further description thereof is consideredunnecessary.

A baule 'il is disposed in passage 65 vsubstantially parallel to wall'i8 separating the smoke receiving passage il@ from the settling out andcooling passage 55. A second baffle 'I9 extends at right angles tobarile il from wall l2 dening a 6 side wall of passage 5B. Baies 11 andlg Cause the smoke stream to flow through a tortuous path in its passagethrough 66, the smoke stream rst flowing vertically downwardly, thenhorizontally at right angles to its initial direction under baiile 17,then vertically through the space between baiiles 'I1 and 19 into theport 8B leading from the exit end of the settling out and coolingpassage 66. As the smoke stream changes its direction of flow, contactsbaille '19, and is caused to pass through the restricted passageway 8lbetween baffles Tl and 19, tarry material, sui.- pended liquid and solidparticles are removed therefrom, the material thus removed gravitatinginto the sump 16.

Water is continuously supplied to sump 'i5 by branch line 15 to providea stream of water flowing over the partitions 82 (Figures 4 and 5) inthe corner of the passage 65. Partitions S2, with the corner of housingill, form a drain box 83 over the top of which water containing tarryand other suspended material continuously flows. Near the base of thedrain box, in the base of side wall i3, is an opening 84 (Figure 7)through which the water flows into a drain box 85 provided with anoverflow 8S. Box 85 is dimensioned such that a column of water ismaintained therein of a height to provide a liquid seal for opening 3d,which lseal adequately prevents escape of smoke through opening 8.

It will be noted from Figure 5 that the sawdust containing compartmentI8 and the smoke generating compartment are disposed in side by siderelationship at one end of housing lil and extend from this end themajor portion of thel length of the housing. The smoke receiving passagei9 and the smoke settling out passage E56 are disposed in side by siderelation at the other end of housing Iii occupying the remaining minorportion of the volume of the housing. Passage @9, as clearly shown inFigure 5, is disposed in longitudinal alignment with compartments El and65 in longitudinal alignment With compartment i8; the top of compartmenti9 through.

port 5l communicates with passage 4Q; the top of passage 4! through fan5i communicates with passage E6; and smoke discharge Dort 86 is disposedat the exit end of passage 65. Hence a compact and simple smokegenerator is provided having a long tortuous path of travel for thegenerated smoke to effect cooling thereof and removal therefrom ofsuspended material, including water added for cooling purposes. Further,the fan (a) furnishes the draft for providing a blast of air to supportcombustion of the sawdust, (b) draws the resultant smoke through theiiue i3 and smoke receiving passage 49, (c) effects mixing of the smokewith air in proportions to produce a smoke of desired density dependingupon setting of dampers 6l and 58, (d) disperses cooling water into thesmoke stream, and (e) forces the resultant smoke stream through settlingand cooling chamber 66 into and through discharge port Se whichcommunicates with one or more smoke houses.

In operation, cool moist sawdust is charged into compartment i8. Themoisture content of the sawdust will depend on the nature of the so drythat the individual particles readily-sepa-` rate when pressed, watershould be added thereto acoge-4e 7. and' the sawdust and water mixed toproduce a moist mass, i. e., one from which water will not drainoif butisV suiciently moist so that the particles when pressed between thefingers tend to lump or agglomerate. Motor 31 is then energized to feedthe sawdust in regulated amounts onto grate. 4|, thev sawdust on thisgrate having previously been ignited. Motor 6B: is energized at the sametime to actuate fan 6| to cause a blast of air to pass through. slots42, the slot arrangement. giving effective distribution of air intocontact with the thin layer of sawdust. on grate 4|. The rate of airblast and sawdust fed is such that the sawdust is transformed into smokeat substantially the same rate as. it is fed by drums. through slot 29.The smoke thus generated flows through ue 43, first down and then. upthrough passage 49 into passageway 63 where it mixes with air drawn intopassageway 63 through passageway 64 by fanr 6I to produce a smoke streamof desireddensity. The resultant smoke stream, if too hot, is cooled bywater dispersed therein by the fanY 6l and if too cool, is warmed bysteam admitted through 'lil'. and then flows through the. tortuous pathin passage 66 exiting through discharge port Bd after tarry material,moistureY and other suspended material has been removed therefrom. Theabove described operation. is continuous, sawdust in chamber I8 beingreplenished when necessary.

If it is desired to reduce the amountof smoke generated, this isaccomplished by` reducing the speed of rotationof drum Sil'and, ifdesired, of fan 6l, the motors driving these units being variable speedmotors so that they can drive the drum and fan, respectively, at anyselected speed. Thesev two motors, the drum 39 and fan 6l are designedso that for a given. speed of the motor driving drum 30A and acorrelated speed of the motor driving fan 6|, a blast of air providingoxygen inexcess of the stoichiometric amount required. to supportcombustion of the thin layer of sawdust maintained-'on grate 4! issupplied to this grate. Once combustion of this thin layer is initiated,theblastof air initially contacting the sawdust particles, due tothearrangement of slots 42V in grate 4l, causesa minor portion of thesawdust to burn, generating high temperatures instantaneously whicheffect liberation of the volatile constituents of the sawdust, producinga maximumy amount'of smoke per unit vweight of. sawdust consumed.

It will be noted the. processof this invention results in the productionof 1a uniform volume of smoke per unit weight ofv sawdustv consumed,which smoke is of. constant density, and that the density of the smokeVcan be changed, if desired. It will be further noted. the smokegenerator embodying this invention is unusually flexible inthat thevolume of smoke generated canreadily be changed by manipulatingthecontrols. for the motors driving the sawdust feed and the fan,requires-.a minimum of attention by the operator, and is compact andVsimple in design and eicient in operation.

The term sawdust is used herein in a broad sensefand is intended toinclude woodchips and chips or dust of' other cellulose materialsuitable for use in generating smokeY for heating comestibles.

Since certain changes in carrying out the above process and in the smokegenerator, which embody the invention, may be made without departingfrom its scope, it is intended that al1 matter contained in the abovedescription or shownv in the accompanying drawing shall be interpretedas illustrative and not in a limiting sense.

Whatfis claimed is:

1. A smoke generator comprising a sawdust receiving compartment, a smokegenerating compartment disposed contiguous to the sawdust receivingcompartment, a grate in the smoke generating compartment, means in thesawdust receiving compartment for feeding sawdust therefrom incontrolled amounts on to said grate, a flue in the topv of the smokegenerating compartment extending substantially the full length thereofand communicating therewith, a smoke receiving passage communicatingwith said flue, a settling out and cooling passage disposed adjacent thesmoke receiving lp-assage, a fan communicating with both of saidpassages for exhausting smoke from the smoke receiving passage and forintroducing the smoke into the settling out and cooling passage, and asmoke discharge port at the exit end of the settling out and coolingpassage.

2. A smoke generator comprising a sawdust receiving compartment, a smokegenerating compartment disposed contiguous to the sawdust receivingcompartment, a grate in the smoke generating compartment, means in thesawdust receiving compartment for feeding sawdust therefrom incontrolled amounts on to the grate in the smoke-generating compartment,a flue in the top of the smoke generating compartment extendingsubstantially the full length thereof and communicating therewith', asmoke receiving passage having an inlet port, said flue leading intosaid inlet port of said smoke receiving passage, a baie in said smokereceiving passage disposed in front of and extending below said inletport to causethe'smoke to flow rst downwardly in said smokereceiving-passage and then upwardly therethrough, a settling out andcooling passage disposed adjacent the smoke'receiving passage, a fancommunicating with both of said passages for exhausting smoke from thesmoke receiving passage and for introducing the smoke into the settlingout and cooling passage, and a smoke discharge .port at the exit end ofthe settling out and cooling passage.

3. A smoke generator for producing smoke for treatment of comestiblescomp-rising an oblong housing, a sawdust receiving compartment, a smokegenerating compartment, said compartments being disposed in side by siderelationship at one end of said housing and occupying a major portion ofthe volume of said housing, said compartments being in communicationwith each other through a narrow elongated slot disposed in a wallseparating said compartments, a grate in the smoke generatingcompartment disposed beneath said narrow elongated slot, means in thesawdust receiving compartment for feeding a regulated amount of sawdustfrom said compartment through said slot on to said grate, av

smoke receiving passage having an inlet port, and a settlingout andcooling passage disposed in side by side relationship therewith at theother end of said housing and occupying the remainder of the volume ofsaid housing, a flue in the top of and extending the length of the smokegenerating compartment and communicating therewith and also with saidinlet port to the smoke receiving passage, a lbaiiie in the smokereceiving passage disposed in front of and extending below said in- `letportto cause the smoke to ow first downwardly in said smoke receivingpassage and then upwardly therethrough, a Vfan communicating with bothof said passages for exhausting smoke from the smoke receiving passageand or introducing the smoke into the settling out and cooling passage,and a smoke discharge port at the exit end of the settling out andcooling passage.

4. A smoke generator for producing smoke for treatment of comestiblescomprising an oblong housing, a sawdust receiving compartment, a smokegenerating compartment, said compartments being disposed in side by siderelationship at one end of said housing and occupying a major portion ofthe volume of said housing,

said compartments being in communication with each other through anarrow elongated slot disposed in a wall separating said compartments, agrate in the smoke generating compartment disposed beneath said narrowelongated slot, means in the sawdust receiving compartment for feeding aregulated amount of sawdust from said compartment through said slot onto said grate, a smoke receiving passage having an inlet port, and asettling out and cooling passage disposed in side by side relationshiptherewith at the other end of said housing and occupying the remainderof the volume of said housing, a nue in the top of and extending thelength of the smoke generating compartment and communicating therewithand also with said inlet port, a baliie in the smoke receiving passagedisposed in front of and extending below said inlet port for causing thesmoke to flow first downwardly into said smoke receiving passage andthen upwardly therethrough, a fan communicating with both of saidpassages for creating a draft through the grate and for exhausting smokefrom the smoke receiving passage and introducing said smoke into thesettling out and cooling passage, and a smoke discharge port at the exitend of the settling out and cooling passage.

5. A smoke'generator for generating smoke for treatment of comestibles,which comprises an oblong housing, a sawdust receiving compartment and asmoke generating compartment disposed in side by side relationship andextending from one end of said housing to near the opposite end thereofacross the full width thereof, high temperature heat insulation on theinner walls of said smoke generator compartment to minimize the transferof heat therefrom to the sawdust in the sawdust receiving compartment,the side wall separating the sawdust receiving compartment from thesmoke generating compartment having an elongated slot 'therein throughwhich the two compartments are in communication with each other, saidslot being disposed near the base of the sawdust receiving compartment,a grate in the smoke generating compartment disposed below said slot, acylinder having a substantial area of its periphery open rotatablymounted in the lower portion of said sawdust receiving compartmentarranged to receive sawdust, means for rotating said cylinder to causesawdust to be fed in regulated amounts through said slot on to saidgrate to form a thin layer of sawdust on said grate, a nue extending thefull length of said smoke generating compartment at the top thereof andcommunicating therewith, a smoke receiving passage having an inlet port,and a settling out and cooling passage disposed in side by siderelationship therewith at the other end of said housing, the exit endor" said flue leading into said inlet port, a baiile in said smokereceiving 'passage disposed in front .of and extending below said inletVport tofcausesmoke nowing from-said flue to flow rst in a downwarddirection then .in an upward direction about said baie through saidsmoke receiving passage, a fan communicating with both of said passagesfor creating a draftl of air through 4Said grate to support combustionof the sawdust supplied thereto and forV exhausting the resulting smokethrough said flue and into and through said smoke receiving passage andintroducing the smoke into the settling out and cooling passage, meansfor supplying water to the fan bearing and fan Ablades to cool the fanbearings, the rotating fan blades dispersing said water into said smoke,awater sump for collecting tarry material and suspended particlesremoved from the smoke disposed at the base of the settling out andcooling passage, and a smoke discharge port at the exit end of thesettling out and cooling passage.

6. A smoke generator for generating smoke for treatment of comestibles,which comprises an oblong housing, a sawdust receiving compartment and asmoke generating compartment disposed in side by side relationship andextending from one end of said housing to near the opposite end thereofacross the full width thereof, high temperature heat insulation on theinner walls of said smoke generator compartment to minimize the transferheat therefrom to the sawdust in the sawdust receiving compartment, theside wall separating the sawdust receiving compartment from the smokegenerating compartment having an elongated slot therein through whichthe two compartments are in communication with each other, said slotbeing disposed near the base of the sawdust receiving compartment, agrate in the `smoke generating compartment disposed below said slot, acylinder having a substantial area of its periphery open, said cylinderbeing rotatably mounted in the lower portion of said sawdust receivingcompartment, an extending portion on said cylinder running substantiallythe full length thereof, means for rotating said cylinder to causesawdust to be fed in regulated amounts through said slot on to saidgrate to form a thin layer of sawdust on said grate, a nue extending thefull length of said smoke generating compartment at the top thereof andcommunicating therewith, a smoke receiving passage having an inlet port,and a settling out and cooling passage disposed in side by siderelationship therewith at the other end of said housing, the exit end ofsaid ue leading into said inlet port, a baie in said smoke receivingpassage disposed in front of said inlet port and extending therebelow tocause smoke flowing from said nue to iiow first in a downward directionthen in an upward direction about said bae through said smoke receivingpassage, a fan, a channel connecting said fan with said smoke receivingpassage, said fan being also connected with said settling out andcooling passage for creating a draft of air through said grate tosupport combustion of the sawdust supplied thereto, for exhausting theresultant smoke from said flue and said smoke receiving passage andintroducing the smoke into said settling out and cooling passage, asecond channel connecting said fan with the atmosphere, a damper in eachof said channels to regulate the relative proportions of air and Vsmokesuppliedby .said 1fan to .-said settling'out Handcoolingmassage, meansrfor supplying Water 4vtothefzam bearings and fan fbladesto 'cool 'thetan bearings; the rotating fan blades .dispersng 'said :waterinto vsaidsmoke, 1a Water sump for collecting tai-ry material fand suspended par-`izioles removed from saidfsmoke disposed at the ibase .of the .settlingout and cooling passage, and a: smoke discharge port at the exit 'endlof `the ysettling out and--coo1ing passage.

CLAUD JS. .MCMULLEN.

12 REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 207,268 Goodin Aug. 20, 1878'1,644,693 Robertson. Oct. 11, 1927 2,072,364 Gray et a1. Mar. 2, 193710 2,2233597 Brewster Dec. 3, .1940

